C

Author: `Dennis Ritchie`_
Date: 1972

C is a general-purpose programming language that `Dennis Ritchie`_ developed between 1969 and 1973 at AT&T Bell Labs, who based it on the earlier languages BCPL and B. [1] C was first used on DEC PDP-11 computers running the newly developed UNIX operating system, where the language provided a high-level alternative to the use of PDP Assembly language for the development of the many utilities that give UNIX its flexibility. [1]

Contents

1   Function

C descends from ALGOL.

The C programming language was invented with the explicit goal of making it easy to port applications from one instruction set to another. C compiles to assembly language.

2   Substance

C is a `procedural language`_ that reflects the philosophy of programming that was taking place during the 1970s (i.e. structured programming). In general, C’s approach can be described as providing the neces- sary features for real world computing in a compact and efficient form. The language provides the basic control structures such as if and switch (see bRanching state- ments) and while, do, and for (see loop). The built-in data types provide for integers (int, short, and long), floating-point numbers (float and double), and characters (char). An array of any type can be declared, and a string is implemented as an array of char. [1]

Data of different types can be combined into a record type called a struct:

struct Employee_Record {
  char [10] First_Name;
  char [1] Middle_Initial;
  char [20] Last_Name;
  int Employee_Number;
};

2.1   Data types

C has four data types, char, double, float, and int, and two modifiers, short and unsigned.

2.2   Header files

Header files contain definitions of data structures and declarations of functions. They must be included in code.

3   History

C was born from taking the `B programming language`_ and adding some good ideas from Pascal_.

4   Further reading

5   References

[1](1, 2, 3) Encycopedia of Computer Science and Technology.